I. Field
The following description relates generally to multicarrier wireless communications systems and more particularly to communication of grants in multicarrier wireless communications systems.
II. Background
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing available system resources (e.g., bandwidth and transmit power). Examples of multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems, orthogonal frequency division multiple access (OFDMA) systems, and so forth.
Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal communicates with one or more base stations through transmissions on forward link and reverse link. Forward link (or downlink) refers to communication link from base stations to terminals, and reverse link (or uplink) refers to communication link from terminals to base stations. These communication links may be established through a single-in-single-out, multiple-in-single-out, or multiple-in-multiple-out (MIMO) system.
A MIMO system employs multiple (NT) transmit antennas and multiple (NR) receive antennas for data transmission. A MIMO channel formed by the NT transmit and NR receive antennas may be decomposed into NS independent channels, which are also referred to as spatial channels, where NS≦min{NT, NR}. Each of the NS independent channels corresponds to a dimension. MIMO systems can provide improved performance (e.g. higher throughput and/or greater reliability) if additional dimensionalities created by multiple transmit and receive antennas are utilized.
A MIMO system supports time division duplex (TDD) and frequency division duplex (FDD) systems. In a TDD system, forward link and reverse link transmissions are on the same frequency region so that the reciprocity principle allows the estimation of forward link channel from reverse link channel. This enables access point to extract transmit beamforming gain on forward link when multiple antennas are available at access point.